A typical image-forming apparatus such as a printer or a copier that uses electrophotographic, ionographic, or magnetographic technologies frequently uses dry powder toner development of an intermediate image created in the image-forming process. Similarly, a printer or other image-forming apparatus that uses thermal inkjet or other liquid ink technologies uses liquid ink to directly form an image on a selected medium. With any of these image-forming technologies, a supply of powder toner or liquid ink is stored in a reservoir from which it is delivered to the image-forming apparatus.
For the case of electrophotographic printing, for example, a photoconductor drum is first electrostatically charged. The photoconductor drum is then exposed to an image light pattern, such as that generated by a laser source, for example, which selectively discharges regions on the previously charged photoconductor drum. The photoconductor drum is developed by delivering electrostatically charged toner particles to the surface of the drum where the charged particles selectively adhere to appropriately charged regions of the drum to form an image corresponding to the image light pattern. The electrostatically transferred toner image is then transferred to paper or other print media and is thermally fused to the paper. Any residual toner is cleaned from the surface of the photoconductor drum prior to reinitiating of the image-forming process. Such a process is applicable to color as well as monochrome printers.
According to the above steps, it is clear that an adequate supply of media marking material such as toner or ink is critical. A lack of toner or ink can result in the onset of unacceptable print quality with consequential waste of resources, such as print media, while the unacceptable quality printing continues. Of course, a lack of toner or ink may also result in a suspension of the print job until the supply of toner or ink is replenished.
Users appreciate knowing the amount of consumable supplies available in a printing device, marking material, for example, especially prior to starting a print or copy job. This is particularly true in the case of a remote printing device in which the user is working at a host computer that is connected via some type of network to the remote printing device. Additionally, it is highly desirable to know and be able to track the amount of marking material consumed, not only on a per printed page or job, but also for a particular imaging apparatus or individual user or users. A user is, typically, unaware of the amount or condition of the consumable supplies, such as toner or ink, available to the printing device prior to sending a print job. A frequent result of this unawareness is finding that the printing device ran out of ink or toner, or other consumable supply, in the middle of a print job at the time the user goes to the printing device to collect the print job. Typically, this results in a waste of both time and resources as the entire print job has to be printed a second time after the printing device has been replenished with the appropriate consumable supplies.
Most printers, copiers, and other imaging devices include the capability to measure or track and report consumable supplies such as ink or toner. Typically, an imaging device incorporates a monitoring or measuring device or sensor to detect and report the toner level in a toner cartridge. Additionally, some imaging devices include the capability to estimate or calculate the amount of marking material used or required to print an image. Typically, an imaging device operates by marking or not marking in a grid pattern of image elements, each element of the grid being referred to as a pel or sometimes as a pixel. It is known to count the number of pels at which toner or ink is printed and the usage of marking material being determined from the number of pels counted. The amount of the beginning or full supply of marking material is known and an estimated remaining marking material is that amount calculated by subtracting the estimated usage.
For conventional imaging devices, such as printers and printer networks, in which the marking material usage is calculated, the calculation is typically performed prior to or during the printing of the print job. In most cases, this calculation can delay or interrupt one or more of the various processing tasks associated with printing the print job. These delays and interruptions can increase the time required to complete a print job thereby decreasing the printer efficiency and production. Additionally, in some printers, toner usage may be measured directly by gauges or sensors coupled directly to the toner or ink cartridge or reservoir. While providing useful information, the amount of toner used for a particular print job is calculated after the fact and is based on a relatively inaccurate measurement of toner remaining in the reservoir.
Accordingly, there is a need for a method of calculating the amount of marking material required to print a print job that provides accurate, advance information and that does not significantly increase the amount of time required to complete the print job.